It is intended to prevent an increase in the quantity of particles on a test-piece substrate having undergone processing executed at a low temperature equal to or lower than 0° C. In an inspection method adopted when inspecting the state inside a processing chamber by measuring the quantity of particles on a test-piece substrate, i.e., a test-piece wafer, the test-piece wafer W having undergone a specific type of test processing inside the processing chamber is carried out into a transfer chamber via a loadlock chamber after holding it in the loadlock chamber over a predetermined length of time while delivering a dried inert gas into the loadlock chamber. The predetermined length of time is set to a value at which the increase in the quantity of particles on the test-piece wafer can be kept down at least within an acceptable range.